The present invention relates to a plasma processing method and apparatus useful in the manufacturing of substrates for semiconductors devices, liquid crystal displays and so on, and more particularly, to apparatus process monitoring techniques useful for controlling process parameters associated with the plasma processing.
For supporting the trend of finer pattern sizes of semiconductor devices, the available scope of process conditions which provide for the realization of uniform processing results within a wafer, that is, a process window, has become narrower year by year in the plasma process. Future plasma processing apparatuses will be required to have the capabilities of more perfectly controlling the process state. The realization of the capabilities would involve an apparatus which is capable of extremely accurately controlling a distribution of a plasma, dissociation of a process gas, and surface reaction in a reactor.
For realizing such a highly accurate control for the plasma processing, some of recent plasma processing apparatuses are equipped with certain monitors for monitoring phenomena in the plasma processing to control the plasma processing using signals from the monitors. Taking a plasma etching apparatus as an example, the most common process monitor is a plasma emission spectrum monitor. For example, Japanese Patent No. 2666768 (JP-A-8-298259) issued on Jun. 27, 1997 discloses a method which relies on a signal generated by a plasma emission spectrum monitor to control a variety of parameters such as RF power, processing pressure, gas flow amount, and so on to manage an etching state. Also, most of currently commercially available plasma etching apparatuses perform an etching end-point determination for determining that etching has been completed using a change in the intensity of light emitted at a particular wavelength, the ratio of intensities of light emitted at a plurality of wavelengths, and so on. In addition, the usefulness of a variety of process monitors such as an impedance monitor for measuring an impedance of a load including a current, voltage and a plasma of a high frequency circuit for generating the plasma, a mass spectrometer, and so on has been investigated, other than the plasma emission spectrum monitor, for higher level plasma processing and management of associated apparatuses. Further, there is a process monitor based on absorption of laser or infrared light at a laboratory level, though it is seldom used in actual manufacturing lines.